Room heating to 28 degrees when stat is on holiday mode and heating in that room shouldn’t come on.

Discussion in 'Plumbers' Talk' started by Chrissymx5, Nov 21, 2020.

  1. Chrissymx5

    Chrissymx5 New Member

    Hopefully all will be revealed tomorrow, Tactfully I’ll mention wiring to him, but I’ll have to be careful,
    being a woman ..........
     
  2. MGW

    MGW Screwfix Select

    My houses have always had a wall thermostat in the coldest room, and TRV's (thermostatic radiator valves) in all other rooms to stop any room overheating, so your looking at the TRV either not working, being set wrong or missing, over temperature is not normally down to wall thermostat.

    I did have a problem in mothers house, and cure was not simple, so I will try to explain in case same with your house.

    Main problem was the sun in a bay window, and the speed at which heating in that room could be turned off/down. So the factors.
    1) Don't want radiators too hot, the hotter it is the longer it takes to cool down, so we you want the boiler if designed to modulate to actually modulate, so circulating water is only just hot enough.
    2) The flow of water through the radiator needs slow, so there is time for the TRV to act before the radiator gets too hot, best if lock shield valve on return, gives the TRV more time.
    3) Need a fast acting valve (TRV head).
    4) Need an easy to understand display showing the temperatures set etc.

    To my mind I, II, III, IIII or *123456 on the side of a TRV is about as much use as a chocolate fire guard. OK 3.5 may be around 20ºC but one needs to know which needs adjusting the lock shield valve or the TRV head, so you want to be able to set the TRV head to 20ºC for example and then adjust the lock shield valve closing if over 20ºC and opening if under 20ºC so your only adjusting one device. So I want a TRV head which shows the temperature in ºC not some silly *123456. So step one is an electronic TRV head.

    So with an electronic TRV head even the cheapest you actually have ºC displayed, so now only adjusting one item, the lock shield valve, found the eQ-3 TRV head at £10 although some can cost £60 each so it depends on what control you want. This 61dmtMm13BL.jpg means you only have the target temperature so you need a thermometer as well, this TRV_report.jpg display on the PC makes it easier as both target and current shown, but that is £10 v £72.99 a pair, don't know why sold as pairs.

    Next stage is linked to the wall thermostat, but now we come to a problem, we want the boiler to modulate, so radiators not too hot and also boiler runs economically, two methods, one return water temperature, the other is a modulating wall thermostat, most boiler manufacturers make a modulating wall thermostat for their boiler, however in the main that will fit in one room, however you have a house split into zones, and to date only wall thermostat I know of which can modulate boiler rather than simple on/off with a zoned system is the EPH thermostat which can be set as master slave, but this means boiler must be OpenTherm and some boilers like Worcester Bosch don't seem to have embraced OpenTherm. And as far as I am aware EPH wall thermostats don't allow connection to TRV heads.

    So it seems either you have to ditch the zone valves, or you have to use return water temperature as the control method.

    Theory you want the programmer to work zone valves and the wall thermostat only works to stop the boiler cycling when we have warm weather, but in practice I have not seen any wiring plan to do this, what we have is a government that has jumped in both feet saying what they want, but not working out how it can be done, so nearly every new installation is a compromise in one way or another. And the use of house and design of house will alter what is the best compromise.

    I don't understand why Screwfix eQ-3 valve is so expensive at £22, I paid £15 for bluetooth version, seen non bluetooth at £10, and I would say try an electronic head first, if then still not good enough the maybe move the cheap one to less critical room and try a linked head. You have not said what boiler or what thermostat so no idea if an OpenTherm one can be used or if already fitted.

    There is one odd one out, Hive wall thermostat is not OpenTherm, but is designed to work with TRV heads with a demand for heat system which allows the boiler to use the return water temperature to control output, however it is the zones which still cause the problem, other than EPH with master/slave I really don't know how zones were ever going to work? My house each room has it's own programmable TRV head so I can reassign a bedroom to be an office or craft room or a dinning room reassigned as a bedroom, I simply can't see how other than separating the likes of a granny flat from rest of house, how a zone valve was intended to work?
     
  3. Chrissymx5

    Chrissymx5 New Member

    Wow, that must have taken you some time to write or did you dictate?
    Sorry but I don’t have radiators, I have underfloor heating, water.
    Thank you for your time.
     

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